1. Field of the Invention
This invention relates to tunnel boring machines, and more particular to the provision of a tunnel boring machine that is adapted to bore through a variety of geological materials, ranging from self-supporting ground to that requiring continuous lining support, and to a boring method.
2. Description of the Prior Art
A known form of machine designed for boring through geological material which is self-supporting is disclosed by U.S. Pat. No. 3,203,737, granted Aug. 31, 1965 to Richard J. Robbins, Douglas F. Winberg and John Galgoczy. This type of machine includes a gripper assembly comprising mechanism which is extendable laterally of the tunnel into anchoring engagement with both sidewall portions of the tunnel. Hydraulic cylinders extend forwardly from the gripper assembly to a frame which supports a power driven cutterhead. These cylinders react rearwardly against the gripper assembly and when they are extended serve to push the frame and the cutterhead carried thereby forwardly in the tunnel. At the end of the stroke the gripper assembly is retracted from the tunnel wall and is pulled forwardly by the cylinders into a new position. It is then extended laterally to take a new grip on the tunnel wall and the process is repeated.
It is also known to tunnel through ground which requires continuous lining support by means of a shield type tunneling machine. An example of a shield type tunneling machine is disclosed by U.S. Pat. No. 3,266,257, granted Aug. 16, 1966 to Raymond J. L. Larrouze, Pierre F. Gesta, Pierre J. M. Goussault, Douglas F. Winberg and Richard J. Robbins. This type of machine includes a tubular body or shield having a rearwardly extending tail section. A sectional tunnel lining is constructed generally behind the machine, within the cover afforded by the tail section. The shield is advanced forwardly during the tunneling operation by the use of a plurality of hydraulic cylinders which are extendable rearwardly from the shield to react against the forward portion of the tunnel lining.
U.S. Pat. No. 3,523,426, granted Aug. 11, 1970 to Ernest Lauber discloses a tunneling apparatus for forming a tunnel through rock having zones differing in stability. According to this patent the tunneling machine (a shield type machine) is used to excavate material. Then, the machine is retracted. Next, a ring of tunnel lining segments is installed in the tunnel forwardly of the machine. Then, the machine is advanced an additional amount. Next, the machine is retracted and another ring of tunnel lining segments is installed. This procedure is repeated until the machine has moved through a zone of soft or unstable material.
U.S. Pat. No. 3,411,826, granted Nov. 19, 1968, to Richard A. Wallers and John C. Haspert, also disclosed a tunnel boring machine which is adapted for boring through both self-supporting ground and ground that requires continuous lining support. It is basically a shield type machine and includes thrust rams which are extendable rearwardly to react against the tunnel lining for shoving the machine forwardly during tunneling through ground requiring a lining. However, the machine is also equipped with an accessory device in the form of a radially expandable ring. When the machine is used for boring through self-supporting ground the ring is installed in the tunnel behind the shield. It is expanded radially for the purpose of tightly gripping the tunnel wall, for the purpose of anchoring it in place in the tunnel. Then, the thrust cylinders are extended rearwardly to react against the anchored ring for moving the machine forwardly in the tunnel relative to such ring.
U.S. Pat. Nos. 3,613,379 and 3,613,384, granted on Oct. 19. 1971, to J. Donovan Jacobs, each discloses a multi-section shield type tunneling machine. The sections are telescopically joined and are each moved in the tunnel relative to the next by means of hydraulic thrust cylinders which may be interconnected between adjacent sections. Also, at least some of the sections are expandable radially to grip the tunnel wall, or carry radially extendable gripper shoes for gripping the tunnel wall. According to these patents, a continuous concrete lining is formed in the tunnel rearwardly of the machine.
An early form of shield tunneling machine is disclosed by U.S. Pat. No. 1,292,159, granted on Jan. 21, 1919, to F. J. Trumpour. It includes inner and outer shields which normally are advanced together by a set of thrust rams which react rearwardly against the forward end of the tunnel lining. When hard material is contacted, the outer shield is still moved forwardly by the thrust rams. The inner shield, which carries power operated cutter elements, is then moved forwardly at a different rate by additional thrust rams which react rearwardly against the outer shield.